In transmitting and receiving data between communications devices in a computer network, reliability is crucial. In order to ensure reliability, circuits that transmit and receive data are often redundant. If an active line goes down a standby line will take over. There are three main models for providing redundant circuits. A description of each follows.
A 1+1 redundancy configuration provides two circuits working in parallel and carrying the same data through two separate physical links. If one interface fails the other takes over. This configuration is the most robust and also the most expensive as it has redundancy not just in the hardware but also for the physical links carrying the data.
A 1:1 redundancy configuration has a device such as an active interface card and one standby card configured in the same manner. As soon as the active interface fails a switch is made to the standby card. The failed card can then be replaced without impacting the data traffic. Typical implementation of such a solution utilizes relays to switch from one interface card to another.
A 1:N redundancy configuration protects N interfaces with a single redundant standby. As soon as one interface fails, the redundant standby takes over. If during this time a second interface fails, then it is not protected. This configuration has a low cost and is often used for a small number of communication lines. The major drawback to this configuration is that a special protection bus is required in hardware to connect the redundant interface to the active interfaces.
The present invention provides a simple and efficient system for implementing 1:1 redundancy in communications devices.